I've followed Gary Onik and think he has some innovative therapies. I know he does focal cryo, and he was also experimenting with IRE. Does he do focal HIFU as well? Almost any kind of ablation can be used for focal salvage.
You have several options other than salvage surgery and salvage ablation.HDR brachytherapy and LDR brachytherapy have been used focally and hemigland for salvage after primary radiation. Here's an article on salvage SBRT:Salvage SBRT for local recurrence after first-line (primary) radiation therapy
I think a mapping biopsy is a great idea, but so is advanced full body PET imaging which should come first (I assume your PSA is above 2) so that you can rule out distant mets.